High resolution electron micrography makes it possible to visualize the micro-structure of carbon black particles. An improved technique, relying on a graphitized carbon black as a calibration specimen, permitted us to establish an accurate distribution pattern of 002d-spacings in carbon blacks. Included were conventional blacks as well as a special thermal black (petroleum coke) untreated, partially and nearly completely graphitized. A technique was developed to microtome single particles. It was found that in untreated blacks, with a low degree of order, a wide, constant distribution of d-spacings exists, independent of the location within the particle. Upon heat treatment, the distribution pattern becomes increasingly narrower and shifts in the direction of smaller d-spacing values, as found in graphitized blacks. Oxidized blacks appear to have greater ordering of carbon planes, due to removal of unorganized fractions; but the d-spacing distribution remains essentially unchanged. Blacks subjected to high energy electrical discharges show a degree of order as in graphitized blacks. It was concluded that the distribution of d-spacings in a carbon black is a reflection of the particle's internal microstructural order.